Numerous aluminum alloys have been proposed in the past for use as anodes in fuel cells, electrochemical couples, and in what is generally referred to as batteries. While some of these alloys are suitable for such use, their preparation and wide use have not become a commercial reality. A major stumbling block in the preparation and commercialization of aluminum alloys and aluminum alloy anode batteries is their relatively high cost because to construct efficient batteries with these aluminum alloy anodes, the aluminum has to be at a very high purity level and the cost of the production of such high purity aluminum becomes prohibitive.
U.S. Pat. Nos. 4,107,406 and 4,150,204 teach an aluminum alloy anode for use in batteries but requires the use of 99.997% pure aluminum, to which other alloying ingredients are added. The production of aluminum at this level of purity requires stringent production control measures and conditions, and cannot be produced by the conventional production reduction cell method. The amount of electricity required to produce aluminum at this level of purity is about twice that used in production cells thus making it very energy-inefficient and prohibitively expensive. Furthermore, the common impurity found in normal production aluminum is iron. Iron is also usually found in other parts of the reduction cell, handling and testing equipment, the walls of the cell and other operating components and processes that it may eventually find its way into the anode alloy. The presence of iron in the form of FeAl.sub.3 in aluminum alloys, even at low levels, creates locations for internal electrochemical reactions between the iron and the aluminum, within the anode itself, thereby reducing the coulombic efficiency of the cell. The prior art method, therefore, requires that in order for the battery to be cost-effective and operate energy-efficiently, the levels of iron impurity must be controlled to be below about 0.02% by weight, which is extremely difficult to achieve.
There is a need, therefore, for an aluminum alloy for use as anode material for batteries which not only exhibits satisfactory electrical properties but which also lends itself to production from a base aluminum as produced in a typical production aluminum reduction cell.
Accordingly, it is an object of the subject invention to provide energy-efficient, cost effective electrochemical cells which utilize aluminum-alloy anodes.
It is another object of the present invention to provide energy-efficient, cost effective electrochemical cells with aluminum-alloy anodes in which the presence of other metals as impurities do not impair the electrical properties of the cells.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.